Two Algorithms for Progressive Computation for Accurate Global Illumination

In this thesis, we present two new algorithms for computing accurate global illumination. These algorithms are general and progressive like path tracing, but provide significant efficiency gains by exploiting coherence in the illumination. The first algorithm reduces the variance of path tracing by filtering the contribution of individual light paths in the image plane. Path space coherence is exploited by spreading the contribution of each path over several pixels. This redistribution is performed using an energy-preserving filter that is constructed based on the local geometry and reflectivity of the environment. The filter size is selected adaptively for each path so as to minimize the noise in the image. A major advantage of our algorithm is its progressive convergence property: the user does not have to specify any parameters that affect the accuracy of the final image because the algorithm can generate and filter additional light paths until the displayed image is sufficiently accurate. The filtering approach is predictive, progressive, general and fully automatic. Therefore, we believe that it can be successfully employed in systems for high quality rendering. The second algorithm is better suited for interactive computation of global illumination in fully dynamic scenes. This algorithm uses a novel scheme for caching the results of a path tracer. The Shading Cache is an object-space hierarchical subdivision mesh with lazily computed shading values at its vertices. A high frame rate display is generated from the Shading Cache using hardware-based interpolation and texture mapping. An image space sampling scheme refines the Shading Cache in regions that have the most estimated error or those that are most likely to be affected by object or camera motion. Our system can efficiently handle dynamic scenes and moving lights, providing useful feedback within a few seconds and high quality images within a few tens of seconds. For the models tested, the Shading Cache significantly outperforms other interactive global illumination systems, especially in dynamic scenes. Based on our results , we believe that the Shading Cache can be an invaluable tool in lighting design and modelling while rendering. Thank you Don for your vision and your leadership, for giving me the chance to work with so many smart people and of course, for the research grants. Some of the research presented in this dissertation was performed in collaboration with Fabio Pellacini and this dissertation would not have taken its present shape without his insights. Thanks also to …